EP1849971B1 - Method for removing pollutants when the engine is stopped - Google Patents
Method for removing pollutants when the engine is stopped Download PDFInfo
- Publication number
- EP1849971B1 EP1849971B1 EP07106653A EP07106653A EP1849971B1 EP 1849971 B1 EP1849971 B1 EP 1849971B1 EP 07106653 A EP07106653 A EP 07106653A EP 07106653 A EP07106653 A EP 07106653A EP 1849971 B1 EP1849971 B1 EP 1849971B1
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- EP
- European Patent Office
- Prior art keywords
- engine
- exhaust gases
- stopped
- air
- discharged
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
- F01N3/30—Arrangements for supply of additional air
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/22—Control of additional air supply only, e.g. using by-passes or variable air pump drives
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
- F01N3/30—Arrangements for supply of additional air
- F01N3/32—Arrangements for supply of additional air using air pump
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/04—Introducing corrections for particular operating conditions
- F02D41/042—Introducing corrections for particular operating conditions for stopping the engine
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2270/00—Mixing air with exhaust gases
- F01N2270/08—Mixing air with exhaust gases for evacuation of exhaust gases, e.g. in tail-pipes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2270/00—Mixing air with exhaust gases
- F01N2270/10—Mixing air with exhaust gases for rendering exhaust innocuous, e.g. by dilution
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2290/00—Movable parts or members in exhaust systems for other than for control purposes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/025—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting O2, e.g. lambda sensors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- F02N11/00—Starting of engines by means of electric motors
- F02N11/08—Circuits or control means specially adapted for starting of engines
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Definitions
- the present invention relates to a method for reducing exhaust gases, including hydrocarbons, in an initial cold start period.
- CO carbon monoxide
- HC hydrocarbons
- NO x nitrogen oxides
- most of the exhaust gases discharged from automobiles are generated in a period of heating a catalyst, that is, a period (cold start period or low-temperature start period) continuing until the temperature of a catalyst reaches an operation temperature (about 300°C ⁇ 450°C), at which a catalyst exhibits optimal catalytic conversion efficiency. Since the cold start spans a time period ranging from several tens of seconds to several minutes, various attempts to minimize exhaust gases during the low-temperature start period have been made.
- the "light-off temperature" in a catalyst is defined as the temperature at the point at which catalytic conversion efficiency surpasses 50%. Only when the temperature of the catalyst reaches the light-off temperature, the catalyst oxidizes both carbon monoxide (CO) and hydrocarbons (HC) and reduces nitrogen oxides (NO x ), thereby converting them into harmless gases.
- CO carbon monoxide
- HC hydrocarbons
- NO x nitrogen oxides
- a method of mounting an electric heater or a burner on a catalyst device that is, a catalyst preheating method, or a method of using heat included in exhaust gases discharged from an engine by closely mounting a catalyst device to an engine, that is, a close mouning method, has been used in order to help a catalyst reach the light-off temperature.
- a method of purifying hydrocarbons in which hydrocarbons (HC), which are discharged in large quantities from an engine and pass through a catalyst device, are adsorbed on a separate trap, and are then discharged from the trap after the temperature of a catalyst reaches the light-off temperature that is, an HC trap method
- the close mounting method has a problem in that, when an engine normally operates, the temperature of a catalyst in the catalyst device increases excessively, thereby decreasing the expected life span of a catalyst.
- the HC trap method has a problem in that durability is reduced.
- the above methods have a problem in that a large amount of precious metals, used to decrease the light-off temperature of a catalyst, entails high processing costs.
- the present invention has been made with the object of reducing automobile exhaust gases in an initial cold start period, which could not been accomplished in spite of the above various attempts and developments.
- the present invention has been completed based on the fact that the concentration of hydrocarbons (HC) measured at the outlet end of catalyst device is higher than the concentration of hydrocarbons (HC) discharged from an engine at the start of engine operation, and on the fact that oxygen included in a catalyst is helpful for purifying hydrocarbons (HC). That is, the present invention has been completed based on the fact that, when the engine start to operate, exhaust gases discharged from the engine are mixed with exhaust gases that were discharged from the engine at the time of previous engine operation and then remain behind, and are then discharged together with them, and, in this case, the exhaust gases can be controlled in an initial cold start period if the previously generated exhaust gases remaining in an exhaust pipe before the start of engine operation can be removed and oxygen can be supplied and stored in this process.
- an object of the present invention is to provide a method for controlling the discharge of air pollutants within a specified range by reducing automobile exhaust gases in a cold start period.
- FIG. 1 A first embodiment not forming part of the present invention will be described in detail with reference to FIG. 1 .
- FIG. 1 shows a system for reducing exhaust gases in an initial start period in an engine 1, which can use fuel such as gasoline, LPG or natural gas, according to the present invention.
- the engine 1 is provided with a suction pipe 2 and an exhaust pipe 3 on the inlet and outlet thereof. Exhaust gases discharged from the engine 1 are guided through a catalyst device including a main catalyst unit 5 provided on the exhaust pipe 3.
- the main catalyst unit 5 has a structure in which a honeycomb ceramic support is coated with a catalytic component mainly composed of any one of platinum group metals or a combination thereof.
- the main catalyst unit 5 include a cylindrical ceramic support of 4.66 ⁇ 6400 cpsi, with a PM weight of 50g/ft 3 an a ratio of Pt to Rh of 5:1.
- An apparatus for reducing exhaust gases includes an air pump 30 which is electrically controllable. Air is supplied to the air pump 30 through a first air channel 31, and the first air channel 31 is connected to the suction pipe 2, located at the inlet end of an air flowmeter 12. The air pump 30 is operated such that the supplied air is injected to the exhaust pipe 3 located upstream of the main catalyst unit 5 through a second air channel 32.
- the second air channel 32 is connected to the exhaust pipe 3 located upstream or downstream of a lambda sensor 8.
- the lambda sensor disposed to detect oxygen included in exhaust gases, is connected to an electronic unit 9 for transmitting signals from the lambda sensor 8 to a compensation unit 10.
- the compensation unit 10 is provided to determine signals related to the mixture of air and fuel and to transmit the signals to an injection unit 11 in the engine 1.
- the injection unit 11 is generally used at the place where the air flowmeter 12 is connected to an apparatus.
- the air pump 30 may include a check valve (not shown) serving to protect the air pump 30 from high-temperature exhaust gases reversely flowing toward the air pump 30.
- the air pump 30 is connected to an output terminal of an electronic switch 7 and a battery 6.
- the air pump 30 is connected to the battery 6 functioning to start an automobile
- the electronic switch 7 is a semiconductor type switch for minimizing damage and supplying electric current to the air pump 30 without danger of the generation of electromagnetic pulses, which is a phenomenon frequently occurring in automobiles.
- the electronic switch 7 may also be a relay type switch.
- an apparatus for reducing exhaust gases includes a computer type control unit 16 designed to be connected to the electronic switch 7 and the air pump 30 and to transmit control signals thereto.
- the control unit 16 serves to monitor an operation of supplying electric current from the battery 6 or a generator (not shown) in automobiles to the air pump 30 based on stop signals transmitted from the engine 1, and serves to control the operation of the air pump 30.
- Exhaust gases discharged from the engine 1 in operation are converted into harmless gases by a catalytic reaction while they pass through the main catalyst unit 5 along the exhaust pipe 3.
- the air pump 30 and the units for controlling the same do not operate during the engine operation period, but the processes for removing pollutants remaining in the exhaust pipe 3 are started by the control unit 16 having received signals from the engine 1 the moment the engine is stopped.
- the electronic switch 7 starts to be operated by the control unit 16 and then operates the air pump 30, and the air pump 30 sucks air from the suction pipe 2 through the first air channel 31 and then injects air into the exhaust pipe 3 through the second air channel 32, thereby pushing exhaust gases remaining in the exhaust pipe 3, located at the inlet end of the main catalyst unit 5, into the main catalyst unit 5. It is preferred that air be injected for 5 ⁇ 10 seconds. When the injection of a predetermined amount of air is completed by the air pump 30, the injection of air is stopped by the control unit 16.
- FIG. 2 is a graph showing the concentration of hydrocarbons (HC) discharged from an engine in an initial start period.
- the concentration of hydrocarbons (HC) discharged from the engine is higher than the concentration of hydrocarbons (HC) discharged through the main catalyst unit in a period of 20 seconds or less.
- the reason is that hydrocarbons (HC) discharged in a previous engine operation remain in an exhaust pipe located at the inlet end of the main catalyst unit.
- "before values” means values measured in a state in which the apparatus for reducing exhaust gases in an initial cold start period according to the present invention is not provided
- “after values” means values measured in a state in which exhaust gases remaining in an exhaust pipe are removed by the apparatus for reducing exhaust gases. As shown in FIG.
- FIG. 3 is a graph showing the accumulated mass of hydrocarbons (HC) measured in FIG. 2 . From the result shown in FIG. 3 , it was found that an effect of reducing hydrocarbons (HC) by an amount of 25% can be obtained.
- a method of reducing exhaust gases includes a first step of determining whether or not engine rotation is stopped; a second step of performing a cranking process by applying a power source to a cranking motor immediately after the engine rotation is stopped in the first step; a third step of turning off a fuel pump while performing the second step; a fourth step of monitoring output values transmitted from an oxygen sensor provided in the inlet end of a main catalyst unit; and a fifth step of stopping the second step in the case where the output values are not more than predetermined values. Accordingly, air is sucked from the exterior concomitantly with the stopping of engine operation, and is then injected into a main catalyst unit, thereby removing exhaust gases including hydrocarbons remaining in the inlet end of the main catalyst unit.
- the engine stop state can be determined by checking whether or not a start switch has been turned off, checking output signals transmitted from an engine speed sensor, or checking output signals transmitted from a water temperature sensor.
- the present invention in a state in which, immediately after the engine is stopped, a process of cranking an engine is performed, and simultaneously an operation of a fuel pump is stopped, thereby preventing fuel from being supplied to a cylinder, residual exhaust gases in previous operations can be discharged by injecting air sucked from the exterior into the inlet end of the main catalyst unit.
- FIG. 4 is a graph showing the state of control variables according to the present invention.
- a fuel pump is stopped, thereby preventing fuel from being supplied to a cylinder.
- a start motor is rotated by an electronic control unit, and the start motor rotates a flywheel. This rotation of the flywheel is transmitted to a crankshaft, and thus reciprocates a piston in a cylinder according to a predetermined cycle.
- the fuel supply is interrupted, only air sucked from the exterior is injected into a main catalyst unit.
- cranking operation When the cranking operation is performed, exhaust gases, such as hydrocarbons (HC), remaining in the main catalyst unit can be discharged to the exterior, and thus the concentration of the discharged hydrocarbons (HC) can be reduced in an initial cold start period.
- the cranking operation may be performed for any predetermined time, but is preferably performed until constant values are obtained by monitoring output values transmitted from an oxygen sensor located at the inlet end of the main catalyst unit.
- step 2 if it is determined that the start key is turned off, an electronic control unit generates signals for operating a cranking motor, and a cranking process is performed in response to the signals (S3), thereby injecting air sucked from the exterior into a main catalyst unit.
- the electronic control unit generates signals for stopping fuel injection simultaneously when the cranking process is performed (S4), thereby stopping fuel supplies to a cylinder through each injector.
- step 3 and 4 When the cranking process is performed in a state in which the supply of fuel is interrupted in step 3 and 4 (S3 and S4), air can be sucked from the exterior, and the sucked air can be injected into an exhaust pipe provided with the main catalyst unit in a state in which it is not mixed with fuel. If output values in a predetermined range are obtained by monitoring the output values transmitted from an oxygen sensor provided at the inlet end of the main catalyst unit (S5), the electronic control unit generates signals for stopping a cranking motor. Then, the operation in the method according to the present invention ends.
- FIG. 6 is a graph showing the concentration of HC discharged from an engine, measured in cold start period, according to the present invention
- FIG. 7 is a graph showing the accumulated concentration of HC discharged from an engine, measured in total periods, according to the present invention.
- the above tests were conducted by applying a Pd/Rh type main catalyst unit. In these tests, the discharge amount of hydrocarbons (HC) in period 1 is reduced at a ratio of 24.5%, and the discharge amount of hydrocarbons (HC) in total periods is reduced at a ratio of 23.8%.
- the method for reducing exhaust gases in an initial cold start period is illustrative.
- the reduction of exhaust gases is accomplished by removing exhaust gases remaining upstream of a main catalyst unit and supplying oxygen to a catalyst immediately after the stop of engine operations.
- an air injection method using cranking operation is described, but is not limited thereto.
- exhaust gases can be removed by sucking exhaust gases remaining in an exhaust pipe and discharging them to the exterior, or can be discharged to the exterior by converting the exhaust gases into harmless gases via a catalytic reaction in the case where a catalyst exists in optimal state by employing some trapping means and reversely discharging the exhaust gases into the exhaust pipe after the temperature of the catalyst reaches a light-off temperature.
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Exhaust Gas After Treatment (AREA)
Description
- The present invention relates to a method for reducing exhaust gases, including hydrocarbons, in an initial cold start period.
- A catalyst device for reducing automobile exhaust gases including carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx), which are principal causes of air pollution, is widely used. However, most of the exhaust gases discharged from automobiles are generated in a period of heating a catalyst, that is, a period (cold start period or low-temperature start period) continuing until the temperature of a catalyst reaches an operation temperature (about 300°C ~ 450°C), at which a catalyst exhibits optimal catalytic conversion efficiency. Since the cold start spans a time period ranging from several tens of seconds to several minutes, various attempts to minimize exhaust gases during the low-temperature start period have been made. For reference, the "light-off temperature" in a catalyst is defined as the temperature at the point at which catalytic conversion efficiency surpasses 50%. Only when the temperature of the catalyst reaches the light-off temperature, the catalyst oxidizes both carbon monoxide (CO) and hydrocarbons (HC) and reduces nitrogen oxides (NOx), thereby converting them into harmless gases.
- Accordingly, a method of mounting an electric heater or a burner on a catalyst device, that is, a catalyst preheating method, or a method of using heat included in exhaust gases discharged from an engine by closely mounting a catalyst device to an engine, that is, a close mouning method, has been used in order to help a catalyst reach the light-off temperature. Further, a method of purifying hydrocarbons in which hydrocarbons (HC), which are discharged in large quantities from an engine and pass through a catalyst device, are adsorbed on a separate trap, and are then discharged from the trap after the temperature of a catalyst reaches the light-off temperature, that is, an HC trap method, has been developed.
- However, the above methods have various problems. For example, the close mounting method has a problem in that, when an engine normally operates, the temperature of a catalyst in the catalyst device increases excessively, thereby decreasing the expected life span of a catalyst. The HC trap method has a problem in that durability is reduced. Further, the above methods have a problem in that a large amount of precious metals, used to decrease the light-off temperature of a catalyst, entails high processing costs.
- The present invention has been made with the object of reducing automobile exhaust gases in an initial cold start period, which could not been accomplished in spite of the above various attempts and developments.
- The present invention has been completed based on the fact that the concentration of hydrocarbons (HC) measured at the outlet end of catalyst device is higher than the concentration of hydrocarbons (HC) discharged from an engine at the start of engine operation, and on the fact that oxygen included in a catalyst is helpful for purifying hydrocarbons (HC). That is, the present invention has been completed based on the fact that, when the engine start to operate, exhaust gases discharged from the engine are mixed with exhaust gases that were discharged from the engine at the time of previous engine operation and then remain behind, and are then discharged together with them, and, in this case, the exhaust gases can be controlled in an initial cold start period if the previously generated exhaust gases remaining in an exhaust pipe before the start of engine operation can be removed and oxygen can be supplied and stored in this process.
- Accordingly, an object of the present invention is to provide a method for controlling the discharge of air pollutants within a specified range by reducing automobile exhaust gases in a cold start period.
- The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
-
FIG. 1 is a schematic view showing an apparatus for reducing exhaust gases. -
FIG. 2 is a graph showing the concentration of HC discharged from an engine -
FIG. 3 is a graph showing the accumulated mass of HC discharged from an engine; -
FIG. 4 is a graph showing the state of control variables according to the present invention; -
FIG. 5 is a flowchart showing a method of reducing exhaust gases according to the present invention; -
FIG. 6 is a graph showing the concentration of HC discharged from an engine, measured in cold start period, according to present invention; and -
FIG. 7 is a graph showing the accumulated concentration of HC discharged from an engine, measured in total periods, according to the second embodiment of the present invention. - Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.
- Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components.
- A first embodiment not forming part of the present invention will be described in detail with reference to
FIG. 1 . -
FIG. 1 shows a system for reducing exhaust gases in an initial start period in anengine 1, which can use fuel such as gasoline, LPG or natural gas, according to the present invention. Theengine 1 is provided with asuction pipe 2 and anexhaust pipe 3 on the inlet and outlet thereof. Exhaust gases discharged from theengine 1 are guided through a catalyst device including amain catalyst unit 5 provided on theexhaust pipe 3. Generally, themain catalyst unit 5 has a structure in which a honeycomb ceramic support is coated with a catalytic component mainly composed of any one of platinum group metals or a combination thereof. In particular, it is preferred that themain catalyst unit 5 include a cylindrical ceramic support of 4.66 × 6400 cpsi, with a PM weight of 50g/ft3 an a ratio of Pt to Rh of 5:1. - An apparatus for reducing exhaust gases according to a first embodiment includes an
air pump 30 which is electrically controllable. Air is supplied to theair pump 30 through afirst air channel 31, and thefirst air channel 31 is connected to thesuction pipe 2, located at the inlet end of anair flowmeter 12. Theair pump 30 is operated such that the supplied air is injected to theexhaust pipe 3 located upstream of themain catalyst unit 5 through asecond air channel 32. Thesecond air channel 32 is connected to theexhaust pipe 3 located upstream or downstream of alambda sensor 8. The lambda sensor, disposed to detect oxygen included in exhaust gases, is connected to anelectronic unit 9 for transmitting signals from thelambda sensor 8 to acompensation unit 10. Thecompensation unit 10 is provided to determine signals related to the mixture of air and fuel and to transmit the signals to aninjection unit 11 in theengine 1. Theinjection unit 11 is generally used at the place where theair flowmeter 12 is connected to an apparatus. Theair pump 30 may include a check valve (not shown) serving to protect theair pump 30 from high-temperature exhaust gases reversely flowing toward theair pump 30. Theair pump 30 is connected to an output terminal of anelectronic switch 7 and abattery 6. - Accordingly, the
air pump 30 is connected to thebattery 6 functioning to start an automobile, and theelectronic switch 7 is a semiconductor type switch for minimizing damage and supplying electric current to theair pump 30 without danger of the generation of electromagnetic pulses, which is a phenomenon frequently occurring in automobiles. Theelectronic switch 7 may also be a relay type switch. - Further, an apparatus for reducing exhaust gases according to the first embodiment includes a computer
type control unit 16 designed to be connected to theelectronic switch 7 and theair pump 30 and to transmit control signals thereto. - The
control unit 16 serves to monitor an operation of supplying electric current from thebattery 6 or a generator (not shown) in automobiles to theair pump 30 based on stop signals transmitted from theengine 1, and serves to control the operation of theair pump 30. - Hereinafter, the functions of the apparatus not forming part of the present invention for reducing exhaust gases in an initial cold start period will be described based on the above constitution.
- Exhaust gases discharged from the
engine 1 in operation are converted into harmless gases by a catalytic reaction while they pass through themain catalyst unit 5 along theexhaust pipe 3. As such, theair pump 30 and the units for controlling the same do not operate during the engine operation period, but the processes for removing pollutants remaining in theexhaust pipe 3 are started by thecontrol unit 16 having received signals from theengine 1 the moment the engine is stopped. Theelectronic switch 7 starts to be operated by thecontrol unit 16 and then operates theair pump 30, and theair pump 30 sucks air from thesuction pipe 2 through thefirst air channel 31 and then injects air into theexhaust pipe 3 through thesecond air channel 32, thereby pushing exhaust gases remaining in theexhaust pipe 3, located at the inlet end of themain catalyst unit 5, into themain catalyst unit 5. It is preferred that air be injected for 5 ~ 10 seconds. When the injection of a predetermined amount of air is completed by theair pump 30, the injection of air is stopped by thecontrol unit 16. - Hereinafter, the efficiency of the purification of exhaust gases, which can be obtained by removing exhaust gases remaining in the exhaust pipe, will be described based on the first constitution, described above.
-
FIG. 2 is a graph showing the concentration of hydrocarbons (HC) discharged from an engine in an initial start period. As shown inFIG. 2 , the concentration of hydrocarbons (HC) discharged from the engine is higher than the concentration of hydrocarbons (HC) discharged through the main catalyst unit in a period of 20 seconds or less. The reason is that hydrocarbons (HC) discharged in a previous engine operation remain in an exhaust pipe located at the inlet end of the main catalyst unit. InFIG. 2 , "before values" means values measured in a state in which the apparatus for reducing exhaust gases in an initial cold start period according to the present invention is not provided, and "after values" means values measured in a state in which exhaust gases remaining in an exhaust pipe are removed by the apparatus for reducing exhaust gases. As shown inFIG. 2 , it was found that the concentration of hydrocarbons (HC) was considerably decreased in a period of 10 ~ 30 seconds in the initial engine start period, compared to that in conventional apparatuses for reducing exhaust gases.FIG. 3 is a graph showing the accumulated mass of hydrocarbons (HC) measured inFIG. 2 . From the result shown inFIG. 3 , it was found that an effect of reducing hydrocarbons (HC) by an amount of 25% can be obtained. - According to the present invention, a method of reducing exhaust gases includes a first step of determining whether or not engine rotation is stopped; a second step of performing a cranking process by applying a power source to a cranking motor immediately after the engine rotation is stopped in the first step; a third step of turning off a fuel pump while performing the second step; a fourth step of monitoring output values transmitted from an oxygen sensor provided in the inlet end of a main catalyst unit; and a fifth step of stopping the second step in the case where the output values are not more than predetermined values. Accordingly, air is sucked from the exterior concomitantly with the stopping of engine operation, and is then injected into a main catalyst unit, thereby removing exhaust gases including hydrocarbons remaining in the inlet end of the main catalyst unit.
- In the first step, various means can be considered in order to determine whether or not engine rotation has stopped. Preferably, the engine stop state can be determined by checking whether or not a start switch has been turned off, checking output signals transmitted from an engine speed sensor, or checking output signals transmitted from a water temperature sensor. In the present invention, in a state in which, immediately after the engine is stopped, a process of cranking an engine is performed, and simultaneously an operation of a fuel pump is stopped, thereby preventing fuel from being supplied to a cylinder, residual exhaust gases in previous operations can be discharged by injecting air sucked from the exterior into the inlet end of the main catalyst unit.
- The present invention will be described in detail with reference to
FIGS. 4 to 5 . -
FIG. 4 is a graph showing the state of control variables according to the present invention. Here, after an engine is stopped, the operation of a fuel pump is stopped, thereby preventing fuel from being supplied to a cylinder. Simultaneously, a start motor is rotated by an electronic control unit, and the start motor rotates a flywheel. This rotation of the flywheel is transmitted to a crankshaft, and thus reciprocates a piston in a cylinder according to a predetermined cycle. However, since the fuel supply is interrupted, only air sucked from the exterior is injected into a main catalyst unit. When the cranking operation is performed, exhaust gases, such as hydrocarbons (HC), remaining in the main catalyst unit can be discharged to the exterior, and thus the concentration of the discharged hydrocarbons (HC) can be reduced in an initial cold start period. The cranking operation may be performed for any predetermined time, but is preferably performed until constant values are obtained by monitoring output values transmitted from an oxygen sensor located at the inlet end of the main catalyst unit. - Hereinafter, the operation in the method according to the present invention will be described in detail with reference to
FIG. 5 . - If operation in the method according to the present invention is started during normal engine operation (S1), whether or not engine rotation is stopped is determined (S2). For example, if a start key is not turned off, subsequent steps are not performed until it is turned off.
- In step 2 (S2), if it is determined that the start key is turned off, an electronic control unit generates signals for operating a cranking motor, and a cranking process is performed in response to the signals (S3), thereby injecting air sucked from the exterior into a main catalyst unit. The electronic control unit generates signals for stopping fuel injection simultaneously when the cranking process is performed (S4), thereby stopping fuel supplies to a cylinder through each injector.
- When the cranking process is performed in a state in which the supply of fuel is interrupted in
step 3 and 4 (S3 and S4), air can be sucked from the exterior, and the sucked air can be injected into an exhaust pipe provided with the main catalyst unit in a state in which it is not mixed with fuel. If output values in a predetermined range are obtained by monitoring the output values transmitted from an oxygen sensor provided at the inlet end of the main catalyst unit (S5), the electronic control unit generates signals for stopping a cranking motor. Then, the operation in the method according to the present invention ends. -
FIG. 6 is a graph showing the concentration of HC discharged from an engine, measured in cold start period, according to the present invention, andFIG. 7 is a graph showing the accumulated concentration of HC discharged from an engine, measured in total periods, according to the present invention. The above tests were conducted by applying a Pd/Rh type main catalyst unit. In these tests, the discharge amount of hydrocarbons (HC) inperiod 1 is reduced at a ratio of 24.5%, and the discharge amount of hydrocarbons (HC) in total periods is reduced at a ratio of 23.8%. - Meanwhile, the method for reducing exhaust gases in an initial cold start period according to the present invention is illustrative. The reduction of exhaust gases is accomplished by removing exhaust gases remaining upstream of a main catalyst unit and supplying oxygen to a catalyst immediately after the stop of engine operations. In the embodiment of the present invention, an air injection method using cranking operation is described, but is not limited thereto. Here, it goes without saying that exhaust gases can be removed by sucking exhaust gases remaining in an exhaust pipe and discharging them to the exterior, or can be discharged to the exterior by converting the exhaust gases into harmless gases via a catalytic reaction in the case where a catalyst exists in optimal state by employing some trapping means and reversely discharging the exhaust gases into the exhaust pipe after the temperature of the catalyst reaches a light-off temperature.
Claims (2)
- A method for removing pollutants when the engine is stopped, in which a main catalyst unit is connected to an engine through an exhaust pipe, comprising:a first step of determining whether or not engine rotation is stopped;a second step of performing a cranking process by applying a power source to a cranking motor immediately after the engine rotation is stopped in the first step;a third step of turning off a fuel pump while performing the second step;a fourth step of monitoring output values transmitted from an oxygen sensor provided in an inlet end of a main catalyst unit; anda fifth step of stopping the second step in the case where the output values are not more than predetermined values.
- The method according to claim 1, wherein, in the first step, the engine stop state is determined by checking whether or not a start switch is turned off, checking output signals transmitted from an engine speed sensor, or checking output signals transmitted from a water temperature sensor.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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KR20060036978 | 2006-04-25 | ||
KR1020060081655A KR100750364B1 (en) | 2006-08-28 | 2006-08-28 | A method of reducing the exhaust gas including hc in the cold start phase by carrying out cranking procedure immediately after engine stop |
Publications (3)
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EP1849971A2 EP1849971A2 (en) | 2007-10-31 |
EP1849971A3 EP1849971A3 (en) | 2007-11-07 |
EP1849971B1 true EP1849971B1 (en) | 2009-11-18 |
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EP07106653A Active EP1849971B1 (en) | 2006-04-25 | 2007-04-20 | Method for removing pollutants when the engine is stopped |
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US (1) | US7895825B2 (en) |
EP (1) | EP1849971B1 (en) |
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US8828325B2 (en) * | 2007-08-31 | 2014-09-09 | Caterpillar Inc. | Exhaust system having catalytically active particulate filter |
US8752366B2 (en) * | 2010-05-21 | 2014-06-17 | Toyota Motor Engineering & Manufacturing North America, Inc. | Systems and methods for abating carbon monoxide in an exhaust stream |
US8806868B2 (en) * | 2011-02-17 | 2014-08-19 | GM Global Technology Operations LLC | Secondary air injection system and method |
US8966896B2 (en) | 2011-07-19 | 2015-03-03 | GM Global Technology Operations LLC | Secondary air injection system and method |
US10578039B2 (en) * | 2017-08-25 | 2020-03-03 | Continental Automotive Systems, Inc. | Proactive catalyst heating |
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JPH03179132A (en) * | 1989-12-06 | 1991-08-05 | Mitsubishi Steel Mfg Co Ltd | Exhaust device of internal combustion engine |
US5459999A (en) * | 1993-07-05 | 1995-10-24 | Mitsubishi Denki Kabushiki Kaisha | Exhaust gas cleaner system for an internal combustion engine with catalytic converter supplied with secondary air |
JP3396378B2 (en) * | 1996-08-15 | 2003-04-14 | トヨタ自動車株式会社 | Method and apparatus for purifying exhaust gas of an internal combustion engine |
JP3631035B2 (en) * | 1999-02-22 | 2005-03-23 | 本田技研工業株式会社 | Exhaust secondary air supply control device for internal combustion engine |
CN1283910C (en) * | 2000-02-25 | 2006-11-08 | 日产自动车株式会社 | Engine exhjaust purification device |
JP2004225539A (en) * | 2003-01-20 | 2004-08-12 | Hitachi Ltd | Exhaust emission control device |
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2007
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US20070245717A1 (en) | 2007-10-25 |
EP1849971A3 (en) | 2007-11-07 |
US7895825B2 (en) | 2011-03-01 |
EP1849971A2 (en) | 2007-10-31 |
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